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From "Michael McCandless (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-2881) Track FieldInfo per segment instead of per-IW-session
Date Tue, 22 Mar 2011 10:01:05 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2881?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13009599#comment-13009599
] 

Michael McCandless commented on LUCENE-2881:
--------------------------------------------

Patch looks great!  Only a few things:

  * We still need a header (id + version) on the fnx file?

  * FieldInfos ctor that loads from index file name but makes a new
    bimap seems spooky...? Is this only used by tests now...?

  * Can you add a comment where we create the N.fnx name, explaining
    why it has no leading _?  (ie, because it's not a per-segment
    file, but rather a global file, shared by multiple segments)

  * In CHANGES entry, persistend is mis-spelled (need to drop the n);
    also remove the _ from _X.fnx, and add . after "successful commit".


> Track FieldInfo per segment instead of per-IW-session
> -----------------------------------------------------
>
>                 Key: LUCENE-2881
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2881
>             Project: Lucene - Java
>          Issue Type: Improvement
>    Affects Versions: Realtime Branch, CSF branch, 4.0
>            Reporter: Simon Willnauer
>            Assignee: Simon Willnauer
>             Fix For: Realtime Branch, CSF branch, 4.0
>
>         Attachments: LUCENE-2881.patch, LUCENE-2881.patch, LUCENE-2881.patch, LUCENE-2881.patch,
lucene-2881.patch, lucene-2881.patch, lucene-2881.patch, lucene-2881.patch, lucene-2881.patch
>
>
> Currently FieldInfo is tracked per IW session to guarantee consistent global field-naming
/ ordering. IW carries FI instances over from previous segments which also carries over field
properties like isIndexed etc. While having consistent field ordering per IW session appears
to be important due to bulk merging stored fields etc. carrying over other properties might
become problematic with Lucene's Codec support.  Codecs that rely on consistent properties
in FI will fail if FI properties are carried over.
> The DocValuesCodec (DocValuesBranch) for instance writes files per segment and field
(using the field id within the file name). Yet, if a segment has no DocValues indexed in a
particular segment but a previous segment in the same IW session had DocValues, FieldInfo#docValues
will be true  since those values are reused from previous segments. 
> We already work around this "limitation" in SegmentInfo with properties like hasVectors
or hasProx which is really something we should manage per Codec & Segment. Ideally FieldInfo
would be managed per Segment and Codec such that its properties are valid per segment. It
also seems to be necessary to bind FieldInfoS to SegmentInfo logically since its really just
per segment metadata.  

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